For connection of optical fibers to be used for optical communications or connection of an optical fiber with e.g. a light-emitting element or a light-receiving element, it is required that before the connection, end faces of the optical fibers are butted to each other or an end face of the optical fiber and e.g the light-emitting element or light-receiving element are butted to each other.
For this purpose, a holder of cylindrical shape called a ferrule is attached to an end portion of the optical fiber, and the holder is inserted into an optical connector or the like for connection. In this case, it is required to cut a part of the optical fiber projecting from the end face of the ferrule so that the cut section will have a smooth surface along the end face of the ferrule.
As to the cutting method, various methods have heretofore been proposed. However, in order to avoid the necessity of polishing the end face of the optical fiber after cutting, a cutting technique has been desired by which the cut section will be smooth.
As one such technique, a method has been proposed in Japanese Unexamined Patent Publication No. 63-168603 wherein an optical fiber is cut by making a cut around a bare optical fiber while applying a tension to the bare optical fiber.
Further, Japanese Unexamined Patent Publication No. 6-148436 discloses a machine for cutting an optical fiber which comprises a ferrule-holding means through which a ferrule is inserted for holding and the slant angle of which is changeable; a chucking means for chucking a forward end portion of the optical fiber projecting from the ferrule; a cutting means for cutting the portion of the optical fiber projecting from the ferrule along the end face of the ferrule; and a slant angle-finely adjusting means for finely adjusting the slant angle of the ferrule-holding means, wherein the slant angle of the ferrule-holding means is finely adjusted by means of the slant angle-finely adjusting means depending upon the type or diameter of the optical fiber, to bend the optical fiber in the vicinity of the end face of the ferrule, and the bending portion is cut by means of the cutting means. The cutting means is constructed so that the optical fiber is cut at the stretched side of the bending portion.
Further, Japanese Unexamined Patent Publication No. 4-123009 discloses a method for cutting a forward end portion of an optical fiber which comprises attaching an optical fiber to a ferrule so that the forward end portion of the optical fiber will slightly project; clamping the forward end of the optical fiber while applying a pulling force to the optical fiber by means of a clamping means; while keeping this state, slanting the optical fiber relative to the central axis of the ferrule from the site corresponding to the forward end face of the ferrule; making a cut at the inner side of the slanting portion of the optical fiber along the forward end face of the ferrule; and then slanting the forward end portion of the optical fiber toward the opposite side while keeping the state where a pulling force is applied to the optical fiber.
However, the cutting method as disclosed in Japanese Unexamined Patent Publication No. 63-168603 is a method for cutting the optical fiber by making a cut around the optical fiber while simply pulling the optical fiber straightforward, and therefore has problems that the length of the cut and the smoothness of the cut section tend to be unstable due to the irregularity of e.g. pulling force or depth of the cut.
Further, in the cutting machine as disclosed in Japanese Unexamined Patent Publication No. 6-148436, an optical fiber is bent and a cut is made at the outer side of the bending portion for cutting. However, since the cut is made at the bending state and, at the same time, the cutting is conducted, the cut section after cutting is unlikely to be perpendicular to the axis of the optical fiber, i.e. in many cases, the cut is made obliquely, which leads to a problem that optical losses are likely to arise.
Further, in the cutting method as disclosed in Japanese Unexamined Patent Publication No. 4-123009, an optical fiber is bent toward a predetermined direction while applying a tension to the optical fiber, and a cut is made at the inner side of the bending portion, and then the optical fiber is bent toward the opposite direction for cutting. However, since a cutter is pressed against the optical fiber to make a cut at such a level that a scratch is simply formed at one portion, there are problems that when the optical fiber is bent toward the opposite direction, the cut section after cutting is unlikely to be perpendicular to the axis of the optical fiber, i.e. in many cases, the cut is made obliquely, as in the above conventional techniques. Further, since the contact point of the cutter and the optical fiber is limited to one point, there is a problem that adequate durability of the cutter can not be obtained.
Accordingly, the object of the present invention is to provide a method for cutting an optical fiber by which a part of the optical fiber projecting from the ferrule is cut off so that the cut section will be smooth and perpendicular to the axis of the optical fiber, and a cutting machine for carrying out the method.